Human Reproduction Text

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In some species, individuals __ during their lifetime; in other species, like sea slugs, an individual is both __ and __.

change their sex

male and female

Other species, like bees, only contain few individuals who can __.
A population outlives its members only by __, the generation of new individuals from existing ones

reproduce

reproduction

a.Two modes of animal reproduction—__and __

i.In sexual: __a.Female gamete: __b.Male gamete: __

sexual

asexual

fusion of haploid gametes-->diploid zygote, which gives rise to gametes by meiosis

egg= large, nonmotile cell

sperm= smaller, motile cell

i.Asexual reproduction: __1.Reproduction relies entirely on __ cell divisionb.Majority of animals carry out __, but some have __like the __and __

generation of new individuals without the fusion of egg and sperm

mitotic

sexual

asexual

rotifer

whiptail lizard

I.Mechanisms of Asexual Reproductiona.Several among invertebratesi.Fission: __ii.Budding: __iii.Gemmules: __iv.Two-step processes1.__a.If more than one piece grows and develops into a complete animal--> __Parthenogenesis

separation of parent organism into two individuals of approx. equal size

new individuals arise from outgrowths of existing ones

Release of specialized group of cells that grow into new individuals (sponges)

1. Fragmentation: breaking of the body into several pieces

2. Regeneration: regrowth of lost body parts

reproduction

asexual reproduction in which an egg develops without being fertilized

Parthenogenesis

asexual reproduction in which an egg develops without being fertilized, such as in bees, wasps, and ants

1.Progeny either haploid or diploid

If haploid: offspring develop into adults that produce eggs and sperm without meiosis

2. Present in every__ species (Komodo dragon)
How did they figure this out?

1/1000

a. Females completely isolated from males of species but still produced offspring

External fertilization:i.Among some species with external, individuals clustered in same area release gametes into water at same time, called __1.In some cases, a chemical signal generated by one individual in releasing gametes triggers __2.In other cases, environmental cues cause __(palolo worm times spawning with season/ lunar cycle)

a.In spring: moon in last quarter, worms break in half, releasing tail segments engorged with sperm or eggsà rise to surface where eggs are fertilized

spawning

others to release gametes

whole population to release at same time

External i.When not synchronous, specific __leading to fertilization of eggs of one female by one male may occur

a.__ (chemicals released by one organism that can influence physiology and behavior of other individuals of the same species) may be used, regardless of type of fertilization

i.Small, __that disperse into environment and are active in tiny amounts

ii.Function as __, enabling some female insects to be detected by males from far away

Pheromones

volatile or water-soluble molecules

mate attractants

Internal Fertilization Pros:

a.Pros: production of fewer gametes; survival of higher fraction of zygotes

Internal fertilization:i.Better zygote survival due to fact that eggs fertilized __are sheltered from __1.associated with mechanisms that provide __and __

internally

predators

greater protection of embryos

parental care of the young

Internal Fertilization:a.rather than secreting a protective eggshell, some animals retain the __for a portion of its development within __i.embryos of marsupials=__ii.embryos of (placental) mammals= __

embryo

female reproductive tract

short period in uterusàembryos crawl out and complete fetal development attached to mammary gland in mom pouch

remain in uterus throughout where they are nourished by mom’s blood supply through the placenta (temp. organ)